1996 Volume 22 Issue 4 Pages 742-749
An experimental work of copper extraction using a tank of 35 dm3 (liquid volume 16 dm3) volume was carried out for the scale-up of a stirred tank extractor for a liquid surfactant membrane process. In the experiment, kerosene solution containing 17 vol. % Span 80 and 110 wt. % LIX 64 N was used as the oil phase. 15.7 mol·dm-3 copper sulfate solution of pH 5.4 and 0.38 mol·dm-3 or 0.5 mol·dm-3 sulfuric acid solution were used as the outer and the inner aqueous phase, respectively. The extraction rate, the break up ratio of the W/O emulsion, and the mechanical entrainment were measured. As a result of a small scale volume, the extraction rate was expressed by the following Equation
- (d ln Ccu·out/dθ) = k'CL·Cs-0.32·We0.3/ (CH+) 0.5
Where k'= 6.9× 10-5m1.5·mol-0.5·s-1Ccu·out is copper concentration in the outer aqueous phase, CL is weight fraction of extractant in kerosene, Cs, is volume fraction of surfactant in kerosene, θ, extraction time, We, Weber number, D, diameter of impeller, N, agitation speed, ρc, density of outer water, σ, surface tension and CH+ is concentration of hydrogen ion. The optimum conditions of a middle scale tank were as follows, (1) agitation speed is 2.8 s-1, (2) pouring rate of the emulsion should be less than 8.33 cm3·s-1, (3) surfactant concentration is 2 vol. % (about 2.5 wt. %), (4) extractant concentration is 3 wt. %.
Under optimum conditions, more than 99.9% of copper in the feed solution was extracted in 10 min., the break up ratio was less than 2% and the mechanical entrainment was less than 8 vol. %. The extraction rate was expressed by the same equation as in the small scale. The entrainment occurred mainly in the phase separation.
